Catching SIGSEGV (Segmentation Faults) in C

catch_segv.cpp

// This code installs a custom signal handler for the SIGSEGV signal
// (segmentation fault) and then purposefully creates a segmentation
// fault. The custom handler `handler` is then entered, which now
// increases the instruction pointer by 1, skipping the current byte
// of the faulty instruction. This is done for as long as the faulty
// instruction is still active; in the below case, that's 2 bytes.

// Note: This is for 64 bit systems. If you prefer 32 bit, change
// `REG_RIP` to `REG_EIP`. I didn't bother putting an appropriate
// `#ifdef` here.


#include<string.h>
#include<signal.h>
#include<stdio.h>


void handler(int nSignum, siginfo_t* si, void* vcontext) {
    printf("segmentation fault\n");

    ucontext_t* context = (ucontext_t*)vcontext;
    context->uc_mcontext.gregs[REG_RIP]++;
}


int main() {
    printf("start\n");

    struct sigaction action;
    memset(&action, 0, sizeof(struct sigaction));
    action.sa_flags = SA_SIGINFO;
    action.sa_sigaction = handler;
    sigaction(SIGSEGV, &action, NULL);

    int* x = 0;
    int y = *x;

    printf("end\n");

    return 0;
}